(1) Field of the Invention
The present invention relates to corrosion-resistive members having corrosion-resistive faces to be exposed to corrosive gases causing ion bombardment. The invention also relates to semiconductor-producing articles using such members as substrates.
(2) Related Art Statement
Following increased capacities in memory of super LSIs, finely working has been being progressing, so that processes requiring chemical reactions have been more widely used. Particularly, halogen-based gases such as chlorine-based gases and fluorine-based gases are used as a deposition gas, an etching gas or a cleaning gas in the semiconductor-producing apparatuses requiring a super clean state.
In the semiconductor-producing apparatus such as a hot CVD apparatus as a heater for heating a wafer in contact with such a corrosive gas, the semiconductor-cleaning gas of a halogen-based corrosive gas such as ClF3, NF3, CF4, HF or HCl is used after the deposition. During the deposition, another halogen-based gas such as WF6 or SiH2Cl2 is also used as a film-forming gas.
Since silicon nitride is a compound containing Si as a main component constituting wafers, silicon nitride as well as Si, SiO2 and SiC are used for members in semiconductor-producing apparatuses, particularly chambers. NGK Insulators, Ltd. disclosed in JP-A 5-251365 that if a silicon nitride sintered body is exposed to a ClF3 gas at high temperatures, its surface state changes to generate particles.
Silicon nitride members are exposed to various environments. For example, in case of etchers, corrosion of the members is accelerated with ion bombardment, or an ingredient in the member is sputtered with plasma ion bombardment, thereby causing pollution of the wafers. Since the design rule approaches 0.1 xcexcm, such problems became more elicit than before.
It is an object of the present invention to provide a corrosion-resistive member comprising a corrosive-resistive face to be exposed to a corrosive gas causing ion bombardment, wherein a sintered body of silicon nitride is used as the corrosion-resistive face to enhance the corrosion resistance of this corrosion-resistive face.
The present invention relates to a corrosion-resistive member, comprising a corrosion-resistive face which is to be exposed to a corrosive gas causing ion bombardment, at least a part of said corrosion-resistive member comprising a sintered body of silicon nitride having an open porosity of not more than 5%, said silicon nitride sintered body constituting said corrosion-resistive face, said corrosion-resistive member having a characteristic that if two auxiliary planes are formed by cutting the corrosion-resistive member to intersect vertically with said corrosion-resistive face and to be located vertically to each other, said two auxiliary planes satisfy the following orientation index between said two auxiliary planes being not less than 0.8 and not more than 1.2, and the following orientation index between the corrosion-resistive face and each of the auxiliary faces being not less than 1.5.
Orientation index between the two auxiliary planes=[Is1(320)/(Is1(320)+Is1(002))]/[Is2(320)/(Is2(320)+Is2(002))]
wherein Is1(320) denotes an intensity of X-ray diffraction at a 320 face of xcex2-type silicon nitride in one xe2x80x9cIs1xe2x80x9d of the auxiliary planes, Is1(002) denotes an intensity of X-ray diffraction at a 002 face of xcex2-type silicon nitride in the auxiliary planes xe2x80x9cIs1xe2x80x9d, Is2(320) denotes an intensity of X-ray diffraction at a 320 face of xcex2-type silicon nitride in the other auxiliary plane xe2x80x9cIs2xe2x80x9d, and Is2(002) denotes an intensity of X-ray diffraction at a 002 face of xcex2-type silicon nitride in the auxiliary planes xe2x80x9cIs2xe2x80x9d.
Orientation index between the corrosion-resistive face and each of the auxiliary planes=[Im(320)/(Im(320)+Im(002))]/[Is(320)/(Is(320)+Is(002))]
wherein Im(320) denotes an intensity of X-ray diffraction at a 320 face of xcex2-type silicon nitride in the corrosion-resistive face xe2x80x9cmxe2x80x9d, Im(002) denotes an intensity of X-ray diffraction at a 002 face of xcex2-type silicon nitride in the corrosion-resistive face xe2x80x9cmxe2x80x9d, Is(320) denotes an intensity of X-ray diffraction at a 320 face of xcex2-type silicon nitride in the auxiliary plane xe2x80x9cIsxe2x80x9d, and Is(002) denotes an intensity of X-ray diffraction at a 002 face of xcex2-type silicon nitride in the auxiliary planes xe2x80x9cIsxe2x80x9d.
Measurements are made according to the following condition.
Measurement instrument: Powdery X-ray diffractometer manufactured by Rigaku Denki
X rays:CuKxcex1 line
Tube voltage: 35 kV
Diffraction angle 2xcex8 at I(320)=61.3xc2x0
Diffraction angle 2xcex8 at I(320)=64.0xc2x0
In the above, for example, the intensity of X-ray diffraction at the 320 face of xcex2 type silicon nitride at the auxiliary face Is1 denotes a measurement value of the diffraction intensity at the 320 face of the xcex2 type silicon nitride when X rays are irradiated upon the auxiliary face Is1 according to a xcex8-2xcex8 method.
These and other objects, features and advantages of the invention will be apparent from the following description of the invention when taken in conjunction with the attached drawings, with the understanding that some modifications, variations and changes could be easily made by the skilled person in the art to which the invention.